1. Field of the Invention
The present invention relates to a safety device against rupture of a rotary shaft. In particular, the present invention relates to a device intended to stop shaft rotation and to prevent broken portions of the shaft from falling. The invention is particularly suitable for the wind-up shafts of raisable curtain doors, wherein the shaft winds up a flexible curtain of cloth or plastics materials directly or wherein the shaft winds up straps which in turn serve to raise the curtain which may, itself, be formed of panels that are rigid or flexible and that are suitable for folding up above the doorway.
2. Discussion of Related Art
Doors which are used in factories and warehouses often have to operate under difficult conditions. For example, they may be required to operate several hundreds or even thousands of times a day, resulting in sudden starting and stopping of the door components. Operation of the door may be interrupted roughly in the event of accidents, shocks, etc. It can happen that a wind-up shaft breaks. Not only may the pieces of the broken shaft fall to the ground, thus constituting a first danger, but also, since the shaft is broken, one of the parts thereof is no longer braked, and since it is thus free to rotate it will necessarily allow any door portions such as straps or curtains that were previously supported to unwind, thus causing the curtain to be unwound on one side. This gives rise to further risks of parts falling. In addition, it also gives rise to the risk that the curtain will tear or be damaged in some other way.